The present invention relates to a centrifugal clutch for use in recreational vehicles, and particularly to centrifugal cam levers that move by centrifugal force to actuate a variable-speed pulley included in the centrifugal clutch. More particularly, the present invention relates to a pivot assembly for mounting a centrifugal cam lever for pivotable movement about an axis in a centrifugal clutch.
Recreational vehicles such as golf carts, snowmobiles, and go-karts are typically provided with a centrifugal clutch assembly that includes a variable-speed pulley. A variable-speed pulley is connected to an engine shaft and typically includes a fixed pulley flange mounted on the engine shaft and a movable pulley flange that is able to slide back and forth along the longitudinal axis of the engine shaft. Typically, a drive belt lies in a V-shaped groove defined between the fixed and movable pulley flanges. When the pulley flanges are closer together, the drive belt is turned at a higher speed. When the flanges are further apart, the drive belt is turned at a lower speed. See, for example, U.S. Pat. No. 3,759,111 to Hoff for a description of a centrifugal clutch with a variable-speed pulley.
A variable-speed pulley of the type disclosed in the Hoff '111 patent is typically actuated to increase the speed of a drive belt coupled to the variable-speed pulley by a plurality of pivotable centrifugal cam lever attached to a circular movable pulley flange of the variable-speed pulley and mounted to lie in spaced-apart relation around the circumference of the circular movable pulley flange. Typically, such centrifugal cam levers are mounted on cylindrical pivot pins as disclosed in the Hoff '111 patent so that each centrifugal cam lever swings outwardly about the longitudinal axis of its cylindrical pivot pin during rotation of the variable-speed pulley about the longitudinal axis of the engine shaft on which the variable-speed pulley is mounted.
One of the wear areas in a centrifugal clutch is the pivot area at the base of each centrifugal cam lever. Centrifugal clutch operational problems develop once a centrifugal cam lever wears on its pivot pin. A conventional stationary pivot pin uses only the area of contact between the pivot pin and its centrifugal cam lever. This bearing area is small due to loading. In addition, increased wear in the pivot area of the centrifugal cam lever causes noisy operation of a centrifugal clutch. Avoidance of such "pivot area" wear would extend the operational life and enhance quiet operation of a centrifugal clutch.
Various bushings, coatings, and platings could be used on a pivot pin in an effort to reduce wear between a centrifugal clutch lever and its pivot pin. All of these options were considered during the development of the present invention and found to be expensive and to produce less than desired results. For example, bushings between pivot pins and centrifugal cam levers wear rapidly because of limited bearing surface area and bearing span. Due to loading, really only one side of the bushing is being used.
What is needed is a pivot assembly for use in supporting a centrifugal cam lever for pivotable movement in a variable-speed centrifugal clutch that is easy to assemble, inexpensive to produce, and is produced with a minimum number of parts. Vehicle manufacturers would appreciate a pivot assembly that additionally reduces wear of the pivot bearing area on the pivot pin and centrifugal cam lever, that reduces wear of a roller that is mounted on a fixed drive spider included in the centrifugal clutch and that is arranged to engage the free-swinging end of the centrifugal cam lever, and that allows a centrifugal cam lever to pivot with substantially the same ease and success after a significant amount of use as it did when it was new.
According to the present invention, a centrifugal actuator is provided for use in a centrifugal clutch. The centrifugal actuator is for use in a centrifugal clutch of the type having a variable-speed pulley including a fixed pulley flange that is configured to define one side of a belt-receiving V-shaped groove and mounted on a rotatable drive shaft. The variable-speed pulley also includes a movable pulley flange that is configured to define another side of the belt-receiving V-shaped groove and mounted to slide axially on the rotatable drive shaft to vary the width of the V-shaped groove. A fixed base or "drive spider" is mounted on the rotatable drive shaft and is configured to carry at least one centrifugal cam lever-engaging roller.
The centrifugal actuator includes a D-shaped pivot pin (in transverse cross-section) with a longitudinal extending flat, a cam lever or swing weight formed to include a D-shaped through-hole, and pivot pin support means on the movable pulley flange. Illustratively, the pivot pin with flat slides through apertures formed in the pivot pin support means and the D-shaped through-hole formed in the cam lever. A head on one end of the pivot pin and a nut threaded onto another end of the pivot pin is used to locate the pivot pin such that the flat on the pivot pin passes through the D-shaped through-hole formed in the cam lever.
In preferred embodiments, the centrifugal actuator includes a cylindrical pivot pin, a centrifugal cam lever, and two pivot pin support mounts. The cylindrical pivot pin has a longitudinal axis, a cylindrical first end having an enlarged head, a second end formed to include a threaded post for receiving a threaded nut, and a central portion therebetween. The central portion includes an elongated flat exterior surface extending along the longitudinal axis of the pivot pin so that a transverse cross-section of the central portion of pivot pin is D-shaped. Illustratively, the flat surface continues along at least a portion of the second end to simplify manufacture of the pivot pin.
The centrifugal cam lever has a base end formed to include a D-shaped pin-receiving opening and an opposite tip end. Illustratively, the D-shaped central section of the pivot pin fits into the D-shaped opening in the cam lever in close fitting relation so that the pivot pin rotates about its longitudinal axis in response to pivoting movement of the centrifugal cam lever about the longitudinal axis of the pivot pin. The tip end of the centrifugal cam lever is configured to engage and "push off" against one of the rollers mounted on the fixed drive spider during operation of the centrifugal clutch. This push off action is sufficient to urge the movable pulley flange in a direction toward the fixed pulley flange while the drive belt lies in the V-shaped groove so as to narrow the width of the V-shaped groove and increase the speed of the drive belt. Thus, pivoting movement of the centrifugal cam lever functions to "actuate" the centrifugal clutch so as to change the speed of a drive belt engaging the variable speed pulley in the centrifugal clutch.
The two pivot pin support mounts are configured to be appended to the movable pulley flange and face away from the fixed pulley flange. The pivot pin support mounts lie in spaced-apart relation to one another and each pivot pin support mount is formed to include a cylindrical pin-receiving opening. A first end of the pivot pin is received in the cylindrical pin-receiving opening of one pivot mount and the second end of the pivot pin is received in the cylindrical pin-receiving opening of the other pivot mount. The "flattened" central portion of the pivot pin is received in the D-shaped opening formed on the base of the centrifugal cam lever so that the pivot pin rotates about its longitudinal axis in response to pivoting movement of the centrifugal cam lever about the longitudinal axis of the pivot pin. Illustratively, the flat exterior surface on the pivot pin is made large enough to make the pivot pin rotate with the cam lever but small enough to ensure that the pivot pin stays centered within the cylindrical pin-receiving openings formed in the pivot pin support mounts. The tip of each centrifugal cam lever is configured to engage one of the rollers on the fixed base during pivoting movement of such centrifugal cam lever about the longitudinal axis of the pivot pin.
Illustratively, the pivot pin has a longitudinal axis of rotation, the pin-receiving openings formed in the pivot pin support mounts each have a central axis, and the flat exterior surface formed on the pivot pin is sized so that the axis of rotation of the pivot pin is coincident with the central axis of the pin-receiving openings formed in the pivot pin support mounts. Additionally, the flat exterior surface formed on the pivot pin is positioned so that a full D-shaped circumference of the pivot pin engages a D-shaped interior surface in the centrifugal cam lever defining the D-shaped opening therein whenever the centrifugal cam lever pivots about the longitudinal axis of the pivot pin during operation of the centrifugal clutch.
Use of the centrifugal actuator in accordance with the present invention, which actuator includes a pivot pin having a D-shaped cross section and a centrifugal cam lever having a D-shaped pivot pin-receiving opening, ensures that the centrifugal cam lever and the pivot pin move as one piece during pivoting movement of the centrifugal cam lever, just as if the cam lever were integrally appended to the pivot pin. This united movement advantageously increases the bearing contact area between the cam lever and the pivot pin. It also advantageously increases the bearing span from the axial length of the area of engagement of the centrifugal cam lever along the pivot pin to the combined axial length of the two pin-receiving openings formed in the pivot pin support mounts plus the distance between the pin-receiving openings.
Increasing the bearing area reduces the wear of the pivot pin. Increasing the bearing span both reduces wear on the pivot pin and further stabilizes the cam lever thereby reducing wear of the roller mounted on the fixed drive spider and permitting a reduction of the number of parts in the assembly. Vehicle owners and vehicle manufacturers would appreciate a pivot assembly that requires fewer parts and that results in less wear of moving and camming parts.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of a preferred embodiment exemplifying the best mode of carrying out the invention as presently perceived.